The present invention relates generally to fluid flow analysis, particularly fluid flow measurement and visualization techniques, and more specifically to improved laser sheets used as part of those techniques.
Particle image velocimetry (PIV) is a particularly useful technique for measuring and visualizing fluid flow. The PIV process suspends tiny tracer particles in a fluid, usually air, and illuminates them with a laser sheet plane. Successive images of the illuminated particles are made, usually with a digital camera, and the successive images can be combined to both visualize and, very importantly, measure the movement of the fluid.
PIV is most often used for analyzing fluid flow near curved surfaces, such as blades and other components of jet engines and other turbomachines.
Fluid flows that are normal, or perpendicular, to a curved surface can usually be easily measured using PIV techniques using a flat laser sheet. Fluid flows parallel to curved surfaces, however, are much more difficult to measure because, among other problems, the distance between the surface and the laser sheet in successive images changes. This is a particular problem for measuring velocimetry.
It is seen, therefore, that there is a need for improved techniques for measuring fluid flows around curved surfaces.